Vaccines containing antigens from more than one pathogenic organism within a single dose are known as “multivalent” or “combination” vaccines. Various combination vaccines have been approved for human use in the EU and the USA, including trivalent vaccines for protecting against diphtheria, tetanus and pertussis (“DTP” vaccines) and trivalent vaccines for protecting against measles, mumps and rubella (“MMR” vaccines).
Combination vaccines offer patients the advantage of receiving a reduced number of injections, which leads to the clinical advantage of increased compliance (e.g. see chapter 29 of reference 1), particularly for pediatric vaccination. At the same time, however, they present manufacturing difficulties due to factors including: physical and biochemical incompatibility between antigens and other components; immunological interference; and stability. Various combination vaccines are disclosed in references 2 to 10.
In 2005, a widely-publicised study [11] reported that the immunogenicity of N. meningitidis serogroup C ('MenC') capsular saccharide conjugate vaccine was diminished when it was administered with a 9-valent S. pneumoniae conjugated saccharide as a combination vaccine. Moreover, diminished responses were seen to both co-administered H. influenzae type b (‘Hib’) conjugate and co-administered diphtheria toxoid. The authors concluded that the ‘Pnc9-MenC’ combination vaccine “may not be a suitable replacement for individual MenC or pneumococcal glycoconjugate vaccines”. Moreover, they suggested that the incompatibility may not be linked to the combined nature of the antigens, and that it is “possible that the administration of the vaccines separately may have had the same effect”.
Thus there remains a need for an immunisation that can protect against MenC and pneumococcus without significant loss of immunogenicity of these two components. There is an additional need for an immunisation that can protect against MenC, pneumococcus, diphtheria and Hib without significant loss of immunogenicity of these four components. More generally, there remains a need for integrating MenC immunisation into existing immunisation schedules.